Yes there can be. I read somewhere that cladiella and sinularia hate each other. I just can't find the link, but I did find this:
http://www.wetwebmedia.com/softcrlcompfaqs.htm
Leather & Colt corals
I have had a beautiful leather coral in my tank for 9 months. It has
grown to about 10 inches long with a "top" that is about 6 inches in
diameter. The top is covered with polyps that look like little straws.
Each polyp is about 3/4 of an inch long and they are tightly packed over
the entire surface of the "top". I have a Midas Blenny that regularly
perches on this coral. When it does, the polyps withdraw, and then
re-extend when the Midas swims away. The fish doesn't seem to bother
the leather at all.
This week I added a Colt coral to my 50 gallon reef tank. It is in the
opposite corner from my Leather coral. The Colt fully extends in the
light and all of it's polyps come out. It seems to be doing very well.
Three days after introducing the Colt to my tank, I noticed that the
Leather coral was starting to look less healthy. It's polyps are more
withdrawn and not fully extended. I have not changed the supplements to
my tank and the water conditions are excellent with plenty of current
and light.
My questions: Even though separated by 20 inches, could the Colt coral
be putting out mucus or chemicals (into the water) that the Leather
coral is having an adverse reaction to? Will the Leather become
accustomed to the Colt coral? Do I need to remove one of the corals?
Thanks for your help, R. Marsh
>>
Very perceptive, and useful observations. Yes to the chemical interaction... and probably no to having to move the animal. I would place a unit of activated carbon in the filter flow path at this point and "hope for the best"... in all likelihood, an equilibrium/truce will be struck between these two soft corals (order Alcyonacea), with the Leather re-opening within a few weeks.
Bob Fenner